1. Field of Invention
At least one embodiment of the invention relates to an uninterruptible power supply (“UPS”), and in particular, to a UPS that includes contacts for connecting the UPS to a power source.
2. Discussion of Related Art
Typically electrical and electronic devices are connected to one or more sources of electrical power that provide energy for their operation, e.g., either AC power or DC power. In the case of the UPS, the power source may include a source of backup power (e.g., a battery) that allows a load connected to an output of the UPS to continue to operate, for example, upon interruption of an AC source that is also connected to the UPS and which under normal circumstances supplies power to the load. The source of backup power may or may not provide energy for normal UPS operation. Thus, many UPS topologies can also operate in at least a “limited” fashion without a connection to the source of backup power provided that at least one source of power is connected to the UPS, e.g., the AC source, to provide a source of power for internal UPS circuitry.
With advances in analog and digital electronics, many sources of electrical power (including portable power sources) now include signal circuitry that may, for example, allow information to be communicated between the power source and a device connected to it. Signal circuits may include one or more of analog circuits, digital circuits, or a combination of analog and digital circuits. Embodiments of signal circuits may include processors. Signal circuits can operate as sensing circuits, control circuits, logic circuits, communication circuits, or any combination of these circuits. Common examples include the communication of signals corresponding to the charge-status, the temperature and other operating parameters of the power source. The device connected to the power source can employ the information provided by the signal circuit to control operation of the power source and/or the device. The information can also be employed to provide feedback to a user of the device, for example, to provide audible alarms and/or to generate feedback that is accessible via a user interface (e.g., an electronic display).
Generally, power sources are connected to devices using connectors that include a fixed number of contacts. The connectors may be included, for example, in a plug affixed to the end of an electrical cord, in a socket included in the power source and/or device, and in an edge connector of a printed circuit board. When the contacts included with the power source are connected to the corresponding contacts included with the device, a conductive path is formed between the power source and the device. In the case of a UPS, for example, a power circuit and a signal circuit included in the UPS may be connected to a power circuit and a signal circuit, respectively, included in the power source.
Historically, very few contacts were required to connect a power source to a device because only two to four conductors and a ground were necessary, in general, to connect the power circuit to the device. Some example power source/device connections include: the connection of a DC power source to a device using two conductors (e.g., a positive conductor and a negative conductor); the connection of a single phase AC power source to a device using one phase conductor, one neutral conductor, and a ground; and the connection of a three-phase wye connected source to a device using three separate phase conductors, a neutral conductor, and a ground.
The connections identified above are the connections that might be used, for example, when connecting the power circuitry of a UPS to a power source. Because signal circuitry generally operates at a reduced voltage relative to the operating voltage of the power circuitry, a limited number of available contacts (if any) included in the connectors used to connect the power source to the device are traditionally available for use with any signal circuitry. As a result, the traditional approaches to connecting a power source and a device do not provide much flexibility for topologies that require the connection of a plurality of circuits (e.g., power circuitry, signal circuitry, etc.).
A current limiting circuit (e.g., a precharge circuit) provides another example of a circuit that typically requires a connection between the power source and the device circuitry. Often, the device that is being connected to the power source includes a large capacitance. The capacitance can cause a large inrush current when the device is connected to the source of power and the capacitance is charged. The inrush current may result in an arc that can damage the contacts of the connector and/or alarm a user who is making the connection. Accordingly, current limiting circuitry (e.g., a precharge circuit) is employed to reduce the amount of inrush current when the device is connected to the source of power, for example, by charging the capacitance more slowly. Where a current limiting circuit is employed, the connection between the power source and the device may be completed in stages where, for example, the current limiting circuit is completed before the power source is fully connected to the device. The current limiting circuit is then bypassed when the power source and the device are fully connected.
The connection of battery-supplied sources of power may contribute to the amount of inrush current seen by a device when it is connected to the source of battery power because of the low impedance of the batteries.
In addition, the contacts of the connectors employed in signal circuitry generally operate at a much reduced voltage relative to the power and precharge circuits because the signal circuitry generally operates at a voltage that is significantly less than the voltage provide by the source of power. As a result, separate contacts in the connector are often used to complete the signal circuitry.
The limited quantity of conductors included in traditional approaches for connecting the power source to the device limits the ability to include connections for both current limiting circuitry and signal circuitry in a single connector. For example, in one such approach, a UPS includes a precharge circuit, power circuitry that is employed when a power source is fully connected to the UPS, and a signal circuit. Prior approaches, however, are not effective in employing the limited number of contacts provided because at least two contacts are generally required to complete the power circuitry, at least one additional contact is required to complete the signal circuit and at least one additional contact is required to complete the precharge circuit.
Commonly assigned pending U.S. patent application Ser. No. 10/690,726 entitled “Uninterruptible Power Supply Systems and Enclosures,” filed Oct. 22, 2003, describes one approach that employs a separate contact for each of the signal circuit and the precharge circuit. The entire contents of U.S. patent application Ser. No. 10/690,726 are herein incorporated by reference.